Rolling bearing assemblies generally include bearing separators. These bearing separators serve to space the rolling elements from one another and may also self retain the rolling elements as a separate subassembly, depending on the type of bearing.
In the case of Conrad ball bearings, the bearing separator is inserted last, after the bearing balls are in place, so there is no need for a separator-ball subassembly. Access for adding the separator may be available from only one side of the bearing, or from both sides. A Conrad bearing in which access for separator installation is only available from one side is shown in U.S. Pat No. 4,420,195. This type of bearing uses a one piece separator having flexible retaining pockets that are force fitted around the bearing balls. Such separators necessarily have incomplete pockets, that is, pockets that do not completely encircle the bearing balls along any plane of the ball. Such separators are easy to mold, however, in that the molding insert around which the incomplete pocket is formed can be fairly easily withdrawn.
If access for installing the bearing separator into a Conrad bearing is available from both sides, a separator having complete pockets, that is pockets that completely encircle some plane through the rolling elements, can be provided. However, in such a case, the bearing separator is split into two parts or halves, such as is shown in U.S. Pat. No. 4,451,098. The two halves of the separator form complete pockets around the bearing balls when they are joined, but require both an additional part and additional assembly step, as compared to one piece cages.
For other types of bearings such as thrust, linear sliding, and split race bearings, a separator-bearing element subassembly is both possible and useful. Bearing retainers having complete pockets are preferred over those having incomplete pockets, since they provide better bearing element retention. Most preferred of all are separators with pockets that are not only complete, but which also conform to a significant portion of the outer surface of the bearing element, since they provide more secure retention. Such pockets are referred to as wrapping pockets. Complete, wrapping pockets may be easily formed by multipiece separators, however, as noted above, one piece separators are preferred.
One piece separators are most frequently made of plastic, since it is relatively inexpensive and, in general, easy to mold. However, one piece plastic separators having complete, wrapping pockets are difficult to mold. The difficulty flows from the fact that the pocket will conform to the molding insert around which the pocket is formed to at least the same degree that it would conform to the bearing element it is designed to hold. This makes it at least as difficult to withdraw the molding insert as it would be to dislodge the bearing element. Furthermore, the molding insert is typically withdrawn from the pocket at a time when the plastic is not fully cooled, and more subject to deformation. One way in which complete, wrapping pockets can be molded is to mold the separator from a relatively soft and yielding material, allowing the insert to be easily withdrawn. Such a design is disclosed in U.S. Pat. No. 4,073,552. This design is limited, however, in that such a soft material will also be limited in how securely it can retain the bearing elements.
Rigid plastic separators may be molded in one piece, with complete pockets, by using a bypass molding technique, as shown in U.S. Pat. No. 4,330,160. However, bypass molded pockets are limited in that their concave inner surface can conform to no more than 180 degrees of the surface of the bearing element, as will be described in detail below, and would thus not be considered to be wrapping pockets.